New Structure in the Shapley Supercluster

Publ. Astron. Soc. Aust., 1999, 16, 113–23.

M. J. Drinkwater1, D. Proust2, Q. A. Parker3, H. Quintana4 and E. Slezak5

1School of Physics, University of New South Wales, Sydney, NSW 2052, Australia Present address: School of Physics, University of Melbourne, Parkville, Vic. 3052, Australia [email protected] 2DAEC, Observatoire de Meudon, 92195 Meudon Cedex, France 3Anglo-Australian Observatory, Coonabarabran, NSW 2357, Australia Present address: Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK [email protected] 4Departamento de Astronomia y Astrosica, Ponticia Universidad Catolica de Chile, Casilla 104, Santiago 22, Chile [email protected] 5Observatoire de Nice, 06304 Nice, Cedex 4, France [email protected] Received 1998 June 10, accepted 1999 March 3

Abstract: We present new radial velocities for 306 bright (R<16) galaxies in a 77 deg2 region of the Shapley supercluster, measured with the FLAIR-II spectrograph on the UK Schmidt Telescope. The galaxies we measured were uniformly distributed over the survey area, in contrast to previous samples which were concentrated in several rich Abell clusters. Most of the galaxies (230) were members of the Shapley supercluster: they trace out two previously unknown sheets of galaxies linking the Abell clusters of the supercluster. In a 44 deg2 area of the supercluster excluding the Abell clusters, these sheets alone represent an overdensity of a factor of 20 02 compared to a uniform galaxy distribution. The supercluster is not attened in the Declination direction as has been suggested in previous papers. Within our survey area the new galaxies contribute an additional 50% to the known contents of the Shapley supercluster, with a corresponding increase in its contribution to the motion of the Local Group.

Keywords: galaxies: clusters, distances and redshifts — large-scale structure of universe

1 Introduction local universe (Scaramella et al. 1989; Raychaudhury 1989), so it is of particular interest to consider its The Shapley supercluster (SSC) has been investigated eect on the dynamics of the Local Group. In by numerous authors since its discovery in 1930 Paper I it was estimated that for 0 =03 and 1 1 (Quintana et al. 1995, hereafter Paper I). It lies H 0 =75kms Mpc the gravitational pull of the in the general direction of the dipole anisotropy of supercluster may account for up to 25% of the the Cosmic Microwave Background (CMB), and is peculiar velocity of the Local Group required to 1 located at 130 h75 Mpc beyond the Hydra-Centaurus explain the dipole anisotropy of the CMB radiation, ' 1 supercluster ( 50 h75 Mpc away from us). It in which case the mass of the supercluster would consists of many clusters and groups of galaxies in be dominated by intercluster dark matter. the redshift range 004

᭧ Astronomical Society of Australia 1999 1323-3580/99/020113$05.00

Downloaded from https://www.cambridge.org/core. IP address: 170.106.202.226, on 29 Sep 2021 at 22:18:09, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1071/AS99113 114 M. J. Drinkwater et al.

We are continuing this project, using data from that have been neglected in previous observations. wide-eld multi-bre spectrographs to measure many In this paper we emphasise our results from these more galaxy redshifts and get a more complete picture regions. of the composition of the supercluster. Our main We selected targets from red ESO/SRC sky aims are rst to dene the real topology of the survey plates scanned by the MAMA machine at SSC (in Paper I it was shown that the SSC is Paris Observatory (as described in Paper II; see signicantly attened, but the real extent of the also Infante, Slezak & Quintana 1996). The elds concentration is not well dened) and second to observed (listed in Table 1) were the standard analyse the individual X-ray clusters that are true survey elds nearest to the centre of the cluster members of the Shapley Supercluster, in order to (13:25:00, 31:00:00 B1950). These covered an area estimate the cluster masses and investigate suspected of 77 deg2, allowing us to probe the limits of the substructure. Additional observations are planned SSC out to radii as large as 8 deg. before we present a full analysis of the dynamics We dened a sample of galaxies to a limit of R<16, (Proust et al. 1999, in preparation). corresponding (assuming a mean B R =15) to In Paper II we presented data from the MEFOS B<175, the nominal galaxy limiting magnitude spectrograph on the European Southern Observatory of the FLAIR-II system. This corresponds to an 360 m telescope. This has 30 bres ina1deg absolute magnitude of MB = 19 at the Shapley 1 diameter eld, so the observations were again mainly distance of 200 h75 Mpc. This gave samples of concentrated on the known clusters, determining for 600–1000 galaxies per eld. We then removed several of them whether they were members of the any galaxies with published measurements in the supercluster or not. NED database or measured by H. Quintana and In this paper we present new data obtained R. Carrasco (private communication, 1997): 46 with the FLAIR-II (Parker & Watson 1995; Parker galaxies for F382, 81 for F383 and 200 for F444. 1997) multi-bre spectrograph on the UK Schmidt For each observing run we then selected random Telescope at the Anglo-Australian Observatory. This subsamples of about 110 targets per eld from the has 90 bres in a 5555 deg2 eld and has allowed unobserved galaxies. When preparing each eld for us to measure a much more uniform distribution of observation at the telescope, we made a further galaxies in the direction of the SSC, avoiding the selection of 80 targets to observe (10 bres being previous bias in favour of the rich clusters. Our data reserved for measurement of the sky background). reveal the existence of a sheet of galaxies connecting This nal selection was essentially random, but we the main parts of the supercluster. We describe the did reject any galaxies too close (less than about sample and observations in Section 2. We present the 1 arcminute) to another target already chosen or a results along with previous measurements in Section 3 bright star. and discuss the signicance of the measurements in We observed a total of 3 elds with the FLAIR-II Section 4. spectrograph in 1997 May and two more in 1998 April. The details of the observations are given in 2 Observations Table 1. In 1997, out of 6 allocated nights, we were Although a large body of galaxy velocity data only able to observe 3 FLAIR elds successfully is available in the literature for the SSC, the due to poor weather and the rst of these was existing samples of redshifts in each cluster are repeated over 3 nights. Field F444 was observed in highly incomplete, even at the bright end of the particularly poor weather, resulting in a much lower luminosity function. We have therefore started a number of measured redshifts. In 1998 we again campaign to obtain complete samples down to the had poor weather, and were only able to observe same magnitude below L for each cluster. Each two elds in an allocation of 8 half-nights. selected cluster has a projected diameter of 25to The data were reduced as described in Drinkwater 30 degrees, so the FLAIR-II system on the UKST, et al. (1996), using the dobers package in IRAF with its 55 55 deg2 eld, is an ideal facility for (Tody 1993). We measured the radial velocities with this project. The very wide eld also permits us the RVSAO package (Kurtz & Mink 1998) contributed to probe the regions between the dominant clusters to IRAF.

Table 1. Journal of FLAIR observations

Date Field RA (1950) Dec Exposure Seeing Weather Nz 00 1997 May 5 F382 13:12:00 35:00:00 18 000s 2–3 cloud 69 00 1997 May 6 F444 13:25:00 30:00:00 15 000s 2–3 cloud 47 00 1997 May 8 F383 13:36:00 35:00:00 18 000s 3–5 clear 73 00 1998 April 25 F383 13:36:00 35:00:00 15 000s 2–3 clear 61 00 1998 April 27 F382 13:12:00 35:00:00 21 000s 3–5 cloud 56

Note: Nz is the number of galaxies with measured redshifts in each eld.

Table 2. Galaxies observed

RA (B1950) Dec Field mR VV RA (B1950) Dec Field mR VV (km s 1) (km s 1) 13:00:143 36:21:34 382 1586 3443 36 13:10:547 35:10:08 382 1499 7527 96 13:00:355 33:42:37 382 1553 23713 68 13:11:021 36:16:46 382 1452 14367 76 13:01:072 36:16:08 382 1432 10298 56 13:11:098 33:39:12 382 1421 15299 49 13:01:285 36:11:57 382 1574 27469 33 13:11:224 33:49:50 382 1463 15355 81 13:01:300 33:36:27 382 1580 21437 126 13:11:235 36:57:36 382 1521 10229 83 13:01:345 37:14:51 382 1561 15818 101 13:11:306 36:55:53 382 1426 10688 59 13:02:114 36:34:14 382 1584 17698 13 13:11:423 33:07:11 382 1446 8889 69 13:02:388 36:15:49 382 1490 37525 71 13:11:543 33:05:46 382 1558 14649 115 13:02:506 34:01:55 382 1586 25647 42 13:12:057 33:29:36 382 1599 30594 115 13:03:019 36:28:58 382 1439 10092 72 13:12:193 32:37:16 382 1551 14280 90 13:03:143 37:20:00 382 1550 14899 97 13:12:239 33:22:29 382 1420 14531 79 13:03:160 35:44:30 382 1570 24066 96 13:12:393 36:55:29 382 1566 10048 85 13:03:281 36:44:17 382 1565 14943 69 13:12:399 32:26:47 444 1415 13869 96 13:03:446 35:40:23 382 1578 14737 72 13:13:133 36:43:06 382 1590 31971 88 13:03:480 33:55:36 382 1562 25475 184 13:13:219 32:37:24 382 1471 15284 88 13:04:032 36:42:55 382 1592 15011 215 13:13:346 35:00:24 382 1581 11473 98 13:04:084 37:06:37 382 1565 14058 47 13:13:379 32:35:56 382 1592 14428 86 13:04:326 35:51:35 382 1453 15099 75 13:13:405 37:12:41 382 1545 14637 23 13:04:469 32:34:17 382 1424 15419 132 13:13:549 32:59:57 382 1508 14315 98 13:04:499 34:09:57 382 1597 18872 37 13:13:598 35:31:47 382 1580 32384 102 13:04:562 37:19:11 382 1531 15024 60 13:14:304 31:33:07 444 1597 14998 126 13:05:122 37:06:25 382 1548 13228 117 13:14:359 33:11:02 382 1426 15334 48 13:05:199 33:00:31 382 1564 10171 150 13:14:379 33:39:08 382 1486 15224 73 13:05:207 34:03:32 382 1569 15174 163 13:14:444 31:20:39 444 1583 15632 176 13:05:231 35:56:31 382 1587 15763 139 13:15:006 32:57:45 382 1593 25689 64 13:05:408 34:09:29 382 1519 15067 78 13:15:087 37:10:05 382 1468 7330 66 13:06:103 37:15:19 382 1590 14312 81 13:15:170 35:32:43 382 1498 3265 94 13:06:347 34:29:38 382 1521 13201 76 13:15:181 29:53:31 444 1534 9769 73 13:06:473 34:25:01 382 1591 18578 77 13:15:186 36:43:14 382 1530 14921 28 13:06:559 35:20:35 382 1540 28284 52 13:15:213 31:45:59 444 1464 4358 114 13:07:072 36:52:20 382 1596 14350 61 13:15:294 37:02:54 382 1506 15014 63 13:07:296 32:36:43 382 1451 9507 81 13:15:385 33:02:17 382 1433 4342 51 13:07:348 34:20:49 382 1577 27522 60 13:16:066 33:09:45 382 1555 13407 47 13:07:483 37:02:06 382 1428 14555 42 13:16:078 31:33:17 444 1420 15641 103 13:08:018 33:42:02 382 1572 15113 95 13:16:173 36:58:20 382 1491 14311 86 13:08:198 32:43:36 382 1587 43801 44 13:16:315 33:02:46 382 1599 15047 69 13:08:201 32:49:07 382 1439 15899 84 13:16:389 33:05:31 382 1594 14960 70 13:08:254 36:24:37 382 1511 3363 89 13:16:389 33:05:31 382 1448 1247 28 13:08:272 33:49:39 382 1572 14837 25 13:16:408 33:15:18 382 1433 14981 98 13:09:019 34:02:24 382 1582 27235 66 13:16:412 33:39:11 382 1517 8432 37 13:09:071 35:47:53 382 1424 10491 54 13:16:495 36:42:34 382 1576 11687 66 13:09:154 37:11:40 382 1559 13069 119 13:17:089 34:02:03 382 1543 23525 110 13:09:193 34:19:50 382 1492 3196 80 13:17:240 34:50:33 382 1564 13924 121 13:09:343 35:04:41 382 1583 23360 77 13:17:288 36:49:52 382 1516 2359 47 13:09:351 37:04:57 382 1596 10414 81 13:17:384 34:04:01 382 1570 15106 145 13:09:390 33:45:40 382 1555 13063 141 13:17:475 33:52:14 382 1572 23532 69 13:09:539 33:06:23 382 1575 23141 79 13:17:530 34:40:14 382 1573 15393 86 13:09:551 35:59:01 382 1504 14386 63 13:18:055 37:00:34 382 1590 15980 78 13:10:136 34:30:54 382 1560 15159 154 13:18:066 27:47:20 444 1597 15326 122 13:10:319 32:40:51 382 1575 29991 72 13:18:156 32:47:18 382 1523 15768 64 13:10:479 33:06:26 382 1599 29645 117 13:18:161 35:20:17 382 1547 15654 85

Table 2 (continued)

RA (B1950) Dec Field mR VV RA (B1950) Dec Field mR VV (km s 1) (km s 1) 13:18:267 34:55:52 382 1519 20402 58 13:25:419 33:44:20 383 1586 24911 114 13:18:313 35:33:05 382 1542 15373 163 13:25:421 33:56:52 383 1588 14661 129 13:18:363 32:30:51 444 1459 14469 110 13:26:144 28:34:52 444 1420 12289 58 13:18:388 35:54:22 382 1502 15345 94 13:26:277 31:47:04 444 1474 14060 114 13:18:507 34:40:34 382 1519 15222 196 13:26:392 31:17:35 444 1403 15430 87 13:18:580 35:16:37 382 1453 13903 170 13:26:529 28:00:28 444 1444 10015 119 13:19:016 33:36:49 382 1583 35049 132 13:27:090 28:59:02 444 1583 14201 114 13:19:076 35:29:36 382 1562 16535 91 13:27:142 27:43:01 444 1512 10237 114 13:19:151 28:06:35 444 1458 14030 85 13:27:226 32:32:55 383 1433 15666 78 13:19:211 34:32:11 382 1554 15664 126 13:27:241 29:14:38 444 1523 14488 30 13:19:268 34:21:31 382 1559 15667 127 13:27:390 34:21:48 383 1595 21467 84 13:19:391 33:06:29 382 1588 3497 96 13:27:513 31:36:28 444 1596 14470 75 13:19:479 35:36:32 382 1550 14747 142 13:28:114 32:21:51 383 1568 15986 64 13:19:541 33:10:27 382 1426 14379 44 13:28:195 32:28:46 383 1573 3468 95 13:20:048 34:47:15 382 1497 7237 96 13:28:325 33:38:26 383 1558 22089 90 13:20:101 32:27:07 382 1478 8503 67 13:28:584 36:41:55 383 1535 14996 97 13:20:131 34:43:27 382 1500 16498 84 13:29:076 36:03:10 383 1533 20314 76 13:20:240 35:03:57 382 1576 14710 59 13:29:145 33:31:57 383 1493 8770 66 13:20:527 35:38:04 382 1480 3792 78 13:29:164 33:03:38 383 1508 13640 98 13:20:533 34:11:58 382 1545 15426 126 13:29:245 33:07:15 383 1471 15243 81 13:20:570 31:26:49 444 1592 15170 63 13:29:334 32:58:55 383 1495 13916 47 13:20:585 27:43:52 444 1454 13674 69 13:29:337 37:15:24 383 1496 15295 29 13:21:041 34:24:00 382 1449 14472 103 13:29:401 33:54:18 383 1587 14770 96 13:21:058 31:55:18 444 1491 15249 107 13:29:409 37:02:12 383 1558 15687 101 13:21:085 29:02:44 444 1563 14096 98 13:29:493 34:53:51 383 1523 15122 39 13:21:305 31:23:03 444 1466 14390 176 13:30:005 34:27:42 383 1547 36879 77 13:21:331 32:37:59 382 1436 14251 135 13:30:007 28:45:40 444 1557 5526 93 13:21:379 29:59:26 444 1443 3634 98 13:30:044 32:54:49 383 1519 15698 50 13:21:398 33:42:58 382 1535 14827 87 13:30:109 32:50:38 383 1462 14951 53 13:21:518 36:02:13 382 1514 10771 96 13:30:134 37:14:36 383 1579 15164 67 13:21:585 34:06:56 382 1504 8371 106 13:30:149 33:02:41 383 1565 14838 115 13:22:022 31:18:01 444 1600 14773 14 13:30:155 34:11:36 383 1484 7491 16 13:22:204 33:39:05 382 1594 27194 132 13:30:199 31:20:49 444 1596 14559 123 13:22:465 36:19:44 382 1534 15208 42 13:30:341 33:41:34 383 1599 22010 143 13:22:565 37:01:27 382 1544 10225 123 13:30:457 31:13:03 444 1497 15201 74 13:23:229 36:47:09 382 1598 19958 150 13:30:533 35:08:58 383 1592 15377 147 13:23:575 31:16:09 444 1600 14660 117 13:31:012 35:07:39 383 1588 21640 89 13:24:047 33:55:06 382 1589 14909 34 13:31:176 31:13:59 444 1586 14842 89 13:24:085 31:56:19 444 1571 13839 84 13:31:178 27:54:11 444 1485 9187 74 13:24:125 29:48:56 444 1488 1866 78 13:31:195 34:48:41 383 1528 14917 69 13:24:150 30:57:58 444 1492 16332 122 13:31:218 32:43:17 383 1443 15177 70 13:24:181 36:49:27 382 1572 14367 76 13:31:252 29:07:15 444 1535 14008 96 13:24:214 37:00:34 382 1562 14520 36 13:31:303 35:09:30 383 1537 9416 65 13:24:282 36:49:27 383 1574 15098 102 13:31:332 31:28:46 444 1489 16271 85 13:24:284 36:14:05 383 1531 14658 62 13:31:397 36:33:12 383 1600 15274 150 13:24:353 32:02:27 444 1548 14176 82 13:31:489 34:46:49 383 1555 2367 21 13:24:589 32:21:44 383 1566 11832 16 13:31:533 34:58:33 383 1535 16579 20 13:25:131 31:30:38 444 1597 15590 96 13:32:174 33:46:46 383 1498 3878 52 13:25:144 32:30:11 383 1586 11585 57 13:32:285 31:10:15 444 1486 14845 86 13:25:201 31:25:21 444 1517 12200 135 13:32:313 33:54:20 383 1418 7208 66 13:25:250 29:59:01 444 1517 12776 81 13:32:489 31:27:42 444 1594 11794 98

Table 2 (continued)

RA (B1950) Dec Field mR VV RA (B1950) Dec Field mR VV (km s 1) (km s 1) 13:32:540 35:18:55 383 1442 15438 54 13:40:334 32:59:43 383 1555 12267 97 13:33:215 36:38:27 383 1517 15135 51 13:40:340 37:23:43 383 1564 11113 52 13:33:378 32:50:15 383 1546 15688 105 13:40:402 34:31:47 383 1508 17030 72 13:33:412 33:49:11 383 1419 3787 43 13:40:420 36:09:58 383 1460 4311 59 13:33:459 28:50:04 444 1416 4516 89 13:40:526 34:49:27 383 1432 16227 183 13:34:056 34:08:42 383 1514 4133 76 13:40:598 35:31:12 383 1438 11637 28 13:34:111 33:34:08 383 1429 13931 87 13:41:147 34:05:19 383 1487 11202 76 13:34:126 28:16:45 444 1590 15262 98 13:41:232 36:22:42 383 1581 11498 46 13:34:284 34:38:09 383 1550 29247 103 13:41:239 33:51:28 383 1521 11818 71 13:34:437 31:37:28 444 1538 11598 98 13:41:473 32:24:12 383 1553 12438 76 13:34:451 34:16:42 383 1567 22108 68 13:41:493 35:11:00 383 1545 37694 72 13:34:496 33:35:55 383 1554 11289 85 13:41:523 33:21:05 383 1432 11063 31 13:34:502 35:14:29 383 1600 15162 89 13:41:555 34:22:45 383 1524 14660 48 13:34:593 35:23:12 383 1468 15695 71 13:42:086 34:58:58 383 1567 17045 66 13:35:152 34:48:29 383 1547 15162 92 13:42:101 32:38:25 383 1577 12085 83 13:35:213 31:41:48 444 1526 14694 127 13:42:251 32:23:47 383 1423 9469 41 13:35:278 35:42:28 383 1550 11327 74 13:42:336 36:31:58 383 1505 11531 64 13:35:470 34:17:07 383 1524 15420 116 13:42:389 35:01:09 383 1579 17237 50 13:35:521 35:13:11 383 1591 14685 37 13:42:561 33:46:54 383 1510 15058 33 13:36:006 36:11:38 383 1466 13789 55 13:43:082 33:29:39 383 1432 11662 44 13:36:044 35:22:16 383 1550 15223 89 13:43:176 34:14:50 383 1567 24806 35 13:36:047 36:20:26 383 1580 13755 74 13:43:292 32:55:23 383 1554 11760 52 13:36:086 32:20:51 444 1476 16298 77 13:43:326 35:50:50 383 1511 11548 27 13:36:159 36:39:42 383 1530 15741 44 13:43:330 32:24:59 383 1536 12884 52 13:36:183 33:47:22 383 1575 21245 28 13:44:020 33:04:05 383 1598 11113 157 13:36:326 35:12:49 383 1547 19147 68 13:44:065 37:12:33 383 1571 11357 50 13:36:433 35:24:54 383 1519 15791 78 13:44:067 35:03:53 383 1523 11453 47 13:36:442 33:45:54 383 1513 15268 76 13:44:156 32:39:29 383 1576 12304 159 13:36:498 35:41:31 383 1549 29346 77 13:44:161 33:08:38 383 1544 11518 77 13:36:561 33:24:07 383 1454 15381 43 13:44:196 33:23:43 383 1587 13010 70 13:36:566 32:49:51 383 1543 15345 135 13:44:228 36:07:31 383 1504 10963 66 13:37:121 32:48:53 383 1543 11841 59 13:44:293 33:21:14 383 1538 16117 48 13:37:148 32:35:15 383 1456 7254 14 13:44:295 32:50:50 383 1499 11694 49 13:37:151 34:05:41 383 1566 21441 89 13:44:568 32:56:05 383 1492 10328 29 13:37:378 33:44:08 383 1591 14867 61 13:45:055 32:37:12 383 1559 11789 80 13:37:399 35:25:16 383 1554 15641 57 13:45:110 33:06:07 383 1435 11901 34 13:37:598 33:53:02 383 1599 15579 30 13:45:188 32:32:24 383 1574 12585 138 13:38:019 33:25:24 383 1547 15167 66 13:45:299 34:26:11 383 1515 13896 88 13:38:124 34:07:13 383 1557 15485 98 13:45:377 35:26:14 383 1590 30107 78 13:38:223 35:24:09 383 1438 15068 85 13:45:479 34:24:28 383 1529 27740 73 13:38:398 34:07:45 383 1556 16973 66 13:45:491 37:14:52 383 1547 11128 83 13:38:408 33:41:14 383 1539 15161 48 13:46:049 32:36:32 383 1439 11603 49 13:38:492 33:49:06 383 1576 14610 47 13:46:054 33:09:44 383 1472 10868 31 13:38:524 35:37:34 383 1488 11378 62 13:46:063 33:43:18 383 1506 11327 35 13:38:572 32:55:58 383 1549 11945 65 13:46:560 35:14:07 383 1560 28576 122 13:39:270 36:56:20 383 1484 11288 31 13:46:599 33:02:31 383 1578 16129 67 13:39:356 34:37:32 383 1561 4454 51 13:47:037 36:30:57 383 1522 30091 89 13:39:437 37:21:55 383 1578 10122 76 13:47:225 32:49:37 383 1435 10522 50 13:39:553 35:55:15 383 1564 21887 155 13:47:381 32:25:54 383 1549 11098 51 13:40:020 34:43:11 383 1507 16170 50 13:47:489 32:38:51 383 1512 11270 37 13:40:268 36:04:17 383 1518 24883 122 13:48:084 35:50:11 383 1546 22610 95

Figure 1—Distribution of galaxies measured with FLAIR-II (squares) in the three UK Schmidt elds (large dashed squares) observed. The coordinate axes are for equinox B1950. Also shown are previously measured galaxies (dots) and known Abell clusters (labelled circles).

Figure 2—Cone diagrams of all known galaxy redshifts in the direction of the Shapley supercluster. Previously published galaxies are plotted as dots; the new measurements are plotted as open squares. The angular scale is enlarged by a factor of 3 for clarity. The distribution in Declination is repeated at the right for comparison without the new measurements.

Redshifts were measured for absorption-featured spectra using the cross-correlation task XCSAO in RVSAO. We decided to adopt as the absorption velocity the one associated with the minimum error from the cross-correlation against the templates. In the great majority of cases, this coincided also with the maximum R parameter of Tonry & Davis (1979). The redshifts for the emission-line objects were determined using the EMSAO task in RVSAO. EMSAO nds emission lines automatically, computes redshifts for each identied line and combines them into a single radial velocity with error. Spectra showing both absorption and emission features were generally measured with the two tasks XCSAO and EMSAO and the result with the lower error used. Figure 3—Histogram of galaxy redshifts in the direction In two spectra with very poor signal (13:05:19 9, of the Shapley supercluster in the region dened by the 33:00:31 and 13:23:229, 36:47:09) the emission three Schmidt elds shown in Figure 1 with a step size of lines were measured manually and a conservative 500 km s 1. The upper histogram is for all the data and the error of 150 km s1 assigned. We measured velocities lower histogram gives just the previously published data. successfully for 306 galaxies in the sample; these are presented in Table 2. 3.1 Foreground Galaxies We have compared the distributions of the galaxies First, in agreement with previous work, we note we measured to the input samples to check that they the presence of a foreground wall of 269 galaxies are fair samples. There is no signicant dierence (Hydra–Centaurus region) at V = 4242 km s1 with in the distributions of the coordinates, but there = 890 km s1 in the range 2000–6000 km s1. is a small dierence in the magnitude distributions This distribution can be related with the nearby in the sense that the measured sample does not cluster A3627 associated with the ‘Great Attractor’ have as many of the faintest galaxies as the input (Kraan-Korteweg et al. 1996). sample. This is to be expected, as these would have the lowest signal in the FLAIR-II spectra, 3.2 Clusters in the Shapley Supercluster but this should not aect our study of the spatial The previous observations reported in Papers I and distribution signicantly. II concentrated on the Abell clusters, clarifying the 3 Results locations of many of them. We reproduce a list of the main clusters in the SSC region in Table 3 Previous studies of the SSC have covered a very large for references and plot their positions in Figure 1. region of sky, but we will limit our analysis in this As noted above, our new measurements concentrate paper to the region of sky we observed with FLAIR- on galaxies outside the rich clusters in this eld. II: the three UK Schmidt elds in Table 1. In some In particular, we observed virtually no galaxies in cases we will further restrict our analysis to the two foreground or background clusters. We compare the southern elds F382 and F383, where our observations distribution of the SSC galaxies to that of the Abell were much more complete. The distribution of these clusters in two velocity slices in Figures 4 and 5. elds and the galaxies we observed is shown in Figure In the near side of the SSC (7580

Figure 4—Galaxies and clusters in the direction of the Shapley supercluster with velocities in the range 7580

number of galaxies away from the rich Abell clusters inter-cluster sample consisting of galaxies in the previously studied. The majority of the galaxies southern elds (F382 and F383) outside the known we observed were part of the SSC, so our principal Abell clusters in the SSC velocity range. We result is that the SSC is bigger than previously eliminated all galaxies within a 05 degree radius thought, with an additional 230 galaxies in the (about 1 Abell radius) of all the clusters shown velocity range 7580

Figure 5—Galaxies and clusters in the direction of the Shapley supercluster with velocities in the range 12 700

the previous data (42 galaxies, 33 expected) gave an overdensity of 13 detected at only 15. The overdensity for the whole SSC including the Abell clusters is, of course, much larger still. These new observations mean that we must modify the conclusions of Paper I about the overall shape of the SSC. In Paper I it was concluded from the velocity distribution of the clusters that the SSC was very elongated and either inclined towards us or rotating. The SSC extends as far as our measurements to the South, so we nd it is not elongated or attened. We now suggest that it is more complex still, being composed of the known Abell clusters embedded in two sheets of galaxies Figure 6—Histogram of all galaxy redshifts in southern of much larger extent. inter-cluster region of the Shapley supercluster with a bin size of 1000 km s 1. The upper histogram is for both our new data and the previously published data; the lower 4 Discussion histogram gives just the old data. For each histogram a Our new observations of galaxies towards the Shapely curve shows the predicted distribution, allowing for the size of the region and the completeness of the samples based on supercluster have, by surveying a large area away a uniform galaxy distribution (Metcalfe et al. 1991). from known clusters, revealed substantial new large

Table 3. Abell clusters in the Shapley region (40 arcmin) inter-cluster elds north of the core of RA (B1950) Dec. cz Name Dist. Ref. the SSC and also nd an overdensity at the SSC (km s 1) velocity. 12:47:12 36:29:00 – 35276 6 N In Paper I the eect of the SSC on the dynamics 12:51:18 26:07:00 – 1633 6 N of the Local Group was estimated. It was found 12:51:36 28:45:00 15 854 3528 4 I that the mass in the cluster could account for at 12:52:54 30:05:00 15 960 3530 4 I least 25% of the motion of the Local Group with 12:54:24 32:39:00 22 454 3531 5 II 12:54:36 30:06:00 16 100 3532 4 I respect to the cosmic microwave background. Our 12:56:18 26:21:00 22 994 1648 – N new data suggest that the SSC is at least 50% more 12:57:00 33:24:00 14 330 S718 4 II massive, with a signicant part of the extra mass 12:58:18 32:10:00 5 007 3537 – N in the closer subregion. The SSC therefore has a 13:05:54 34:18:00 27 551 3542 14 II more important eect on the Local Group than 13:05:54 34:18:00 39 393 354224 II 13:08:36 33:49:00 22 245 3545 6 II previously thought, although we defer a detailed 13:11:36 29:11:00 22 634 3549 5 II calculation until we have additional data (Proust 13:12:24 33:23:00 17 688 S726 5 I et al. 1999, in preparation). 13:16:06 31:33:00 14 818 3552 6 I 13:16:24 36:55:00 15 110 3553 4 I 13:16:42 33:13:00 14 570 3554 4 II 13:18:00 28:43:00 14 810 3555 4 I Acknowledgments 13:18:42 35:32:00 14 960 S729 5 I We wish to thank Roberto de Propris for kindly 13:20:12 34:37:00 15 140 S731 4 II 13:21:18 31:24:00 14 130 355614 B providing the software to calculate the predicted 13:21:18 31:24:00 15 066 355624 B galaxy n(z) distributions, and we are grateful 13:22:06 28:37:00 14 270 355715 II to the sta of the UKST and AAO for their 13:22:06 28:37:00 23 084 355725 II assistance in the observations. This research was 13:23:00 36:59:00 20 806 S733 - N partially supported by the cooperative program 13:24:06 26:51:00 10 368 173613 I 13:24:06 26:51:00 13 357 173623 I ECOS/CONICYT C96U04, and HQ acknowledges 13:25:06 31:14:00 14 403 3558 3 B support from a Presidential Chair in Science. MJD 13:26:58 31:21:00 14 841 1327 - N acknowledges receipt of an AFCOP travel grant and 13:27:06 29:16:00 13 812 3559 4 I a French Embassy Fellowship in support of visits 13:28:38 31:33:43 12 868 1329 - I to the Paris Observatory, where some of this work 13:29:00 32:58:00 13 864 3560 3 I 13:30:42 31:25:00 14 492 3562 3 B was carried out. 13:31:30 34:58:00 14 930 3564 3 I This research has made use of the NASA/IPAC 13:33:48 33:43:00 3 268 3565 - N Extragalactic Database (NED), which is operated by 13:36:06 35:18:00 15 469 3566 4 II the Jet Propulsion Laboratory, California Institute 13:39:24 26:01:00 32 048 1771 - N of Technology, under contract with the National 13:43:54 37:40:00 11 152 3570 - N 13:44:36 32:37:00 11 730 3571 2 I Aeronautics and Space Administration. 13:45:18 33:08:00 12 142 3572 - N 13:46:18 30:03:00 4 227 3574 - N 13:49:42 32:38:00 11 242 3575 4 II References 13:51:30 27:36:00 14 870 3577 4 II 13:54:42 24:29:00 11 152 3578 3 II Bardelli, S., Zucca, E., Malizia, A., Zamorani, G., Scaramella, R., & Vettolani, G. 1996, A&A, 305, 435 References: I: Quintana et al. (1995, Paper I); II: Quintana et Bardelli, S., Zucca, E., Zamorani, G., Vettolani, G., & al. (1997, Paper II); N: NASA/IPAC, Extragalactic Database Scaramella, R. 1998, MNRAS, 296, 599 (NED; B: Bardelli et al. (1998) Bardelli, S., Zucca, E., & Zamorani, G. 1999, in Observational Cosmology: The Development of Galaxy Systems, Sesto 1998 (astro-ph/9811015) structures in the region. The cluster is part of a Drinkwater, M. J., Currie, M. J., Young, C. K., Hardy, E., & Yearsley, J. M. 1996, MNRAS, 279, 595 much larger structure than was apparent from the Infante, L., Slezak, E., & Quintana, H. 1996, A&A, 315, 657 previous observations, extending uniformly in two Kraan-Korteweg, R. C., Woudt, P. A., Cayatte, V., Fairall, sheets over the whole region we surveyed to the south A. P., Balkowski, C., & Henning, P. A. 1996, Nature, of the core of the SSC. We detected an additional 379, 519 230 members of the SSC in our whole survey area, Kurtz, M. J., & Mink, D. J. 1998, PASP, 110, 934 Metcalfe, N., Shanks, T., Fong, R., & Jones, L. R. 1991, representing a 50% increase on the previous total MNRAS, 249, 498 of 492 SSC galaxies. Our measurements to the Parker, Q. A., & Watson, F. G. 1995, in Wide Field Spec- north of the cluster were much less complete (only troscopy and the Distant Universe, 35th Herstmonceux one eld in poor weather) so we cannot exclude Conference, ed. S. J. Maddox & A. Aragon-Salamanca the possibility that these sheets of galaxies extend (Singapore: World Scientic), p. 33 Parker, Q. A. 1997, in Wide Field Spectroscopy, 2nd equally to the north. Recent results presented by Conference of the Working Group of IAU Commission 9 Bardelli, Zucca & Zamorani (1999) support this on Wide Field Imaging, ed. E. Kontizas et al. (Dordrecht: possibility: they have measured galaxies in 18 small Kluwer), p. 25

Pierre, M., Bohringer, H., Ebeling, H., Voges, W., Schuecker, Raychaudhury, S. 1989, Nature, 342, 251 P., Cruddace, R., & MacGillivray, H. 1994, A&A, 290, Scaramella, R., Baiesi-Pillastrini, G, Chincarini, G., Vet- 725 tolani, G., & Zamorani, G. 1989, Nature, 338, 562 Quintana, H., Ramirez, A., Melnick, J., Raychaudhury, S., Tody, D. 1993, in Astronomical Data Analysis Software and & Slezak, E. 1995, AJ, 110, 463 (Paper I) Systems II, ASP Conf. Ser., Vol. 52, ed. R. J. Hanisch Quintana, H., Melnick, J., Proust, D., & Infante, L. 1997, et al. (San Francisco: PASP), p. 173 A&A Suppl, 125, 247 (Paper II) Tonry, J., & Davis, M. 1979, AJ, 84, 1511